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Hi all! I've been lurking a while and decided to copy/paste my build thread from another forum. It starts off with a history of the MJ - forgive me if all of you are more familiar with it than I am, but if nothing else, it shows the background of why I bought this particular truck! Since CC won't accept so much quotes in one post, I'll be separating some of my relevant posts by date and breaking this up to keep it under the character limit. Notice out the timeline I occasionally mentioned and compare it to what I've actually achieved. Depressing for me, comedic for everyone else. Also, it appears that this truck was discussed here before I owned it (and yes, the sticker is staying). :yes: September 5, 2012 This thread is terribly anticlimactic for the time being, but I thought I’d get it ready for the engine build & swap taking place over the next two or three weeks. I’m hoping to have it and the trans installed, broken in, and ready for the drive to Barber Vintage Festival in October. The early ‘80s marked a transition from full-sized, V8 SUVs to lighter-duty offerings based on smaller truck platforms. When Reagan took office, GM was developing the S10 Blazer and Ford the Bronco II, but American Motors lacked a truck smaller than the Eisenhower-era SJ. Only its Concord/Spirit/Gremlin-based Eagle, powered by the ‘60s-era straight six and featuring a legitimate transfer case, slotted in below the venerable CJ series; however, it lacked the capacity and capability of its larger stablemates. As such, the United States’ lit’lest automaker began work on a small SUV that retained off-road capabilities while using components common to its siblings and other manufacturers’ supply chains. This became the 1984 Jeep Cherokee (XJ), a distinctive design that mated a unibody with an integrated ladder structure - indicative of SUV design practices until the “crossover” trend neutered all the good things about everything in the early ‘00s. The XJ was perched atop a four-link “Quadralink” front and leaf-sprung rear solid axle, rounded out with driveline, steering, and control components pulled from existing Ford, GM, Peugeot, and then-parent Renault parts bins. It's an obvious conclusion. Also, no pants. All this effort notwithstanding, AMC still lacked a compact pickup to compete with the Ranger, S10, and increasingly-competitive Japanese counterparts. The full-sized S/J-series (underpinning the Grand Wagoneer) was twenty years old and the long-wheelbase CJ-8 “Scrambler” had failed to find a market. The solution presented itself in a common platform to be built alongside the XJ in Toledo, Ohio. By developing a high-capacity ladder-frame rear section that slotted into the XJ unibody, AMC retained almost all four-door XJ components from the B-pillar forward aside from floorpan changes required to accommodate the unusual marriage of monocoque and ladder. This Comanche (MJ) was sold in parallel with the XJ for seven model years (’86-’92) and received updates accordingly, including an updated variant of AMC’s early-‘60s straight six after the first model year. Short-wheelbase, six-foot-bed models dominated, while a seven-foot bed offered a Metric Ton payload option for 1987. Even ads neglected to mention the available GM V6 in '86 When a newly-revived Chrysler purchased AMC for its Jeep and Eagle divisions in 1987, a step-sibling rivalry emerged between the independently-developed MJ and Dodge Dakota. Notable was the fact that “Dakota” entries in Baja were re-paneled MJs, which themselves claimed manufacturer's championship titles under the controls of Tommy & Bobby Archer and Walker Evans for SCCA and SCORE, respectively: While nearly three million XJs would roll off the Toledo, Ohio, production line by the time US production ended in 2001 (overseas until 2006), the MJ was discontinued after the 1992 model year with less than 200,000 produced. Less than 6,000 featured the '91+ updates. As Chrysler intended to replace the aging XJ Cherokee with the larger, unrelated 1992 ZJ Grand Cherokee, it originally made financial sense to focus on the Dodge Dakota rather than produce an orphaned XJ-based truck. Ballooning sales of the XJ Cherokee cancelled Chrysler’s 1992 euthanization of the platform to the extent that it received minor changes in ’96-’97 before all manufacturing capability was shipped overseas in 2001. I didn’t set out to find an MJ, as I’m already saturated with 4WD XJs. The plan was originally to find a ’94-’96 LT1 Roadmaster wagon, but after looking at flawless, one-owner 30k-mile examples, I couldn’t see myself actually using it for anything aside from long trips and autocross comedy. I wanted a project, not a time capsule, regardless of how smooth and suave the capsule may be. As such, the goal was simple: find a rust-free, manual ‘87+ MJ. The ’86, whether fuel-injected 2.5L AMC I4 or godawful carbureted 90-degree 2.8L GM V6, is undesirable due a firewall incompatible with the long AMC straight six (allegedly the work of an engineer who wanted to see the six phased out). ‘89.5+ examples were preferred since they saw the addition of an Aisin AX-15 in place of the troublesome Peugeot BA-10/5. ’91/’92 models received Chrysler’s open cooling system and a much-needed electrical update, replacing the maligned Bendix/Renault “Renix” ignition system and cable-operated gauges with something befitting the nineties. The rare Renault 2.1 TD was also a strong option, but two exist in pieces spread across three continents. Enter a rust-free 1990 2WD, short-wheelbase Comanche in Charleston, SC. With a build date a week too early to receive the Chrysler updates, it comes equipped with a knocking 4.0L and Aisin AX-15 that won’t shift when hot, but brake lines, calipers, drums, stater, alternator, exhaust, clutch, and other bits are all new - roughly $3500 of parts & labor since August 2011. The owner decided to pass it along when the engine developed a horrible top-end rattle, but remained steadfast in finding a good home dedicated to reviving the truck rather than parting it. I promptly roped my patient girlfriend into driving my autist self many hours to retrieve this blue beast under the guise of fresh seafood and the beach. After picking up the truck, FSM, a thick stack receipts, and documentation from the friendliest, most helpful couple you could ever meet, I trekked off in a truck that wouldn’t shift and made single-digit oil pressures at 2500RPM. People turned and stared at the source of this racket when it passed. At best, a collapsed lifter was the sole problem; at worst, oil pump and bearing clearances had increased to the extent that the top end was starving. Solid bet on the latter. Radio promptly replaced with functioning OEM Though otherwise clean, those pop-out vent windows guaranteed a surly find: Only a few through holes... leaking MC and forty pounds of wet carpet pad didn't help. Patched and POR-15'd After driving the truck 2500 miles with negligible oil pressure, once adding five quarts of oil to top off the six-quart capacity (rest was in the airbox), the decision was made to pull a junkyard 1994 4.0L with an external-slave AX15 to rebuild while continuing to (ab)use the existing driveline. It made a suitable transport for the 396,000-mile donor: Ground up the speedo cable with that weight in the bed... Only looks to be a clean driveline Although a friend offered me an SLP LS1 and T56 pulled from a late WS6 for a pittance, I made the poor decision to stay the AMC course with my ’94 donor driveline. (In retrospect, the LS swap would have cost roughly the same even after Novak adapters were bought.) This itself bore a surprise, likely explaining why an XJ equipped with a new clutch was sitting in Pull-A-Part: Not my pliers. I'm guessing they were left in there during a clutch job. The engine was torn down and dropped off at a good machinist with the intention of using a 258 crank for a stroker. More on that later. Around this point I gutted a junkyard XJ Limited of all its distinguishing interior & exterior bits to create a trim package that never existed. Also found a clean, matching MJ headliner. "Chrome won't getcha home", etc. Wet spot is somehow not the rear main seal And stripped & refurbished a nasty pair of XJ bucket seats and tilt column. Thus far all work has been either cosmetic or only mildly mechanical, but when the year-old internal slave cylinder (the source of my shifting woes) blew itself in a USPS parking lot, the decision was made to use the external slave bellhousing and shift fork purchased previously. This is where the truck sits currently. The plan!: channeling the spirit of the Archer brothers’ SCCA arrangement above while keeping the truck true to its daily-driver, motorcycle-totin’ roots. Throw some lower-profile tires on the 15x7" steelies and autocross it on Wednesday nights. Keep total investment under $4.5-5k. The ’94 HO block (taken 0.030” over), head, crank, and blueprinted rods should be ready within the coming week. If a set of 258 rods (5.875”) can be procured, I’ll use them with a 258 crank and cast pistons to build a stroker; if not, I’ll stick with the 242 crank and rods (6.125”) to avoid the additional cost of forged, offset-wristpin pistons. Using a ‘96+ main bearing girdle and painting everything AMC engine blue. I’m going for an 8.8:1 CR and associated DCR/quench (might as well leave my induction options open). Was hoping for 250hp/320lbfts stroked, but will gladly settle for that turbo'd. Open cooling system conversion is compiled and ready to go in. Eliminate the nest of vacuum lines wherever possible, largely mirroring the changes Chrysler made for '91. Later models lost EGR due to a different cam grind, and I’m taking out the R12 AC system since Asheville is pretty temperate and my XJ has strong AC. Mopar external slave/master cylinder will enable replacement without dropping the trans, but it’s so vastly superior to the internal arrangement (for which only Chinese replacements are available) that replacement shouldn’t be necessary for many years. Dana 35 rear to be replaced with a Chrysler 8.25” with discs from a KJ Liberty. Spring perches will need to be re-welded, as the MJ is spring-under, XJ 8.25” is spring-over, and KJ 8.25 is coil spring. Axle-mounted load-sensing brake proportioning valve is getting the boot. Dual-piston MC, booster, and knuckles from a WJ Grand Cherokee should improve braking and steering response tremendously, while swaybars from a V8 ZJ Grand Cherokee and some budget Monroes will reduce body roll. I do worry that I’ll incite some snap oversteer with this setup, especially since the stock MJ leaves are terribly prone to axle-wrap. The SCCA teams used fiberglas monoleaves, so I'll have to make due with a pair of steel packs I'm piecing together. So please forgive the slow progress while I get my parts in line! It's certainly not as impressive or involved as the majority of folks' projects, but I think it's a unique approach to take with an uncommon truck. Part 2 to follow.

I bought an 88 Comanche a few weeks ago and I am swapping everything from my XJ into it (entire drivetrain, lift, axles, etc.) I knew the floor had some rust but when I pulled the carpet I found this: Which is suprising because the rest of the Comanche is extremely solid, besides the driver side door, there is literally no rust anywhere else. The black square on the passenger side is a patch someone welded in at some point. The driver side had some sheet metal self-tapped in. So, my question is: Should I por15 it or, since I have a donor XJ at the ready, cut that guy to pieces and weld those pieces into the comanche (I have a friend who is very good at welding)? Is my case too bad for por15? If I do por15 do I cut out all rust everywhere or just sand and wire brush it or just use their cleaners and then put it right on the rust? How much will I need? Any tips, suggestions, links, stories, etc. would be very greatly appreciated!